Tunable Negative Permittivity in Graphene/Poly(Vinylidene Fluoride) Composites with Low Percolation Threshold

Recently, metamaterials with fascinating dielectric behavior have drawn much attention for their potential applications. Herein, percolating graphene/poly(vinylidene fluoride) (GR/PVDF) composites consisting of GR sheets homogeneously dispersed in PVDF matrix are fabricated via hot-pressing method in 20 Hz-1 MHz frequency regions, of which simultaneously realizing negative permittivity with low percolation threshold. It is demonstrated that the negative permittivity of GR/PVDF composites is resulted from the low-frequency plasma oscillation of free electrons, and a universal regulatory mechanism of the Drude model is analyzed. At the same time, rapid formative 3D GR conductive networks contributed to the low percolation threshold (7.78 wt%) of composites. Moreover, it is shown that electrical percolation occurs in samples as GR content exceeds percolation threshold, indicating a typical metal-like behavior. In addition, the reactance is discussed according to the equivalent circuit analysis. This work constructed the metacomposites with low filler content, which is a benefit for practical applications in electromagnetic devices. The percolating graphene/poly(vinylidene fluoride) (GR/PVDF) composites are prepared by hot-pressing method with realizing negative permittivity. It is demonstrated that negative permittivity of GR/PVDF composites is attributed from the low-frequency plasma oscillation of free charges, and a universal regulatory mechanism of the Drude model is analyzed. Moreover, the electrical percolation occurs in GR/PVDF composites, indicating a typical metal-like behavior.image (c) 2023 WILEY-VCH GmbH